Non-breeding gonadal testosterone production of male and female Northern Cardinals (Cardinalis cardinalis) following GnRH challenge

M. Susan DeVries, University of Southern Mississippi
Aaron L. Holbrook, University of Southern Mississippi
Caitlin P. Winters, University of Southern Mississippi
Jodie M. Jawor, University of Southern Mississippi

Abstract

Yearly, testosterone (T) levels fluctuate as many vertebrates cycle through reproductive and non-reproductive periods. Among many temperate birds, it is well established that levels of T peak as gonads recrudesce for breeding and then fall as gonads regress prior to the non-breeding season. While the tissues producing breeding season T are well studied, the tissues responsible for non-breeding T have received less investigative attention. We examined the ability of male and female Northern Cardinals (Cardinalis cardinalis) to elevate gonadal T following standardized injections of gonadotropin-releasing hormone (GnRH) across three non-breeding seasons. Males and females were capable of significantly elevating gonadal T production following GnRH injections during periods of reproductive quiescence. The magnitude of T elevation varied across the non-breeding season, but not between sexes. To our knowledge, this is the first report of a significant increase in gonadal T production following GnRH injections administered in the non-breeding season. (C) 2011 Elsevier Inc. All rights reserved.